Details

Autor(en) / Beteiligte

• El-Sherry, Shiem
• Ogedengbe, Mosun E.
• Hafeez, Mian A.
• Barta, John R.

Titel

Divergent nuclear 18S rDNA paralogs in a turkey coccidium, Eimeria meleagrimitis, complicate molecular systematics and identification

Ist Teil von

• International journal for parasitology, 2013-07, Vol.43 (8), p.679-685

Ort / Verlag

England: Elsevier Ltd

Erscheinungsjahr

2013

Link zum Volltext

Quelle

MEDLINE

Beschreibungen/Notizen

• •Two highly divergent 18S rDNA loci (Types A and B) were identified in the turkey coccidium Eimeria meleagrimitis.•Intraspecific variation of 18S rDNA of E. meleagrimitis exceeds interspecific variation between E. necatrix and E. tenella.•Chimeric sequences, combining portions of different 18S rDNA types, can confound molecular systematics and identification.•Cytochrome c oxidase subunit I (COI) partial sequences are more reliable species-level molecular markers than 18S rDNA. Multiple 18S rDNA sequences were obtained from two single-oocyst-derived lines of each of Eimeria meleagrimitis and Eimeria adenoeides. After analysing the 15 new 18S rDNA sequences from two lines of E. meleagrimitis and 17 new sequences from two lines of E. adenoeides, there were clear indications that divergent, paralogous 18S rDNA copies existed within the nuclear genome of E. meleagrimitis. In contrast, mitochondrial cytochrome c oxidase subunit I (COI) partial sequences from all lines of a particular Eimeria sp. were identical and, in phylogenetic analyses, COI sequences clustered unambiguously in monophyletic and highly-supported clades specific to individual Eimeria sp. Phylogenetic analysis of the new 18S rDNA sequences from E. meleagrimitis showed that they formed two distinct clades: Type A with four new sequences; and Type B with nine new sequences; both Types A and B sequences were obtained from each of the single-oocyst-derived lines of E. meleagrimitis. Together these rDNA types formed a well-supported E. meleagrimitis clade. Types A and B 18S rDNA sequences from E. meleagrimitis had a mean sequence identity of only 97.4% whereas mean sequence identity within types was 99.1–99.3%. The observed intraspecific sequence divergence among E. meleagrimitis 18S rDNA sequence types was even higher (approximately 2.6%) than the interspecific sequence divergence present between some well-recognized species such as Eimeria tenella and Eimeria necatrix (1.1%). Our observations suggest that, unlike COI sequences, 18S rDNA sequences are not reliable molecular markers to be used alone for species identification with coccidia, although 18S rDNA sequences have clear utility for phylogenetic reconstruction of apicomplexan parasites at the genus and higher taxonomic ranks.